~ keep jsont in Types for trivial types

not sure about this

src/types.ml

@@ -30,6 +30,10 @@ module Config_types = struct
   end
 end
 
+module HashCode = struct
+  type t = string
+end
+
 (* https://docs.taler.net/core/api-common.html#tsref-type-ErrorDetail *)
 module ErrorDetail = struct
   (* TODO GANA error codes
@@ -63,7 +67,11 @@ module RelativeTime = struct
     | Forever
 end
 
-module Amount = Amount
+module Amount = struct
+  include Amount
+
+  let jsont = Jsont.of_of_string ~kind:"Amount" of_string ~enc:to_string
+end
 
 (* TODO key format
    - check what is the exact format in GNUNET
@@ -83,6 +91,7 @@ module EddsaPublicKey = struct
     | Ok pub -> Ok pub
 
   let to_b32 pub = pub |> Mirage_crypto_ec.Ed25519.pub_to_octets |> B32.encode
+  let jsont = Jsont.of_of_string ~kind:"EddsaPublicKey" of_b32 ~enc:to_b32
 end
 
 module EddsaSignature : sig
@@ -91,6 +100,7 @@ module EddsaSignature : sig
   val sign : key:Mirage_crypto_ec.Ed25519.priv -> string -> t
   val of_b32 : string -> (t, string) result
   val to_b32 : t -> string
+  val jsont : t Jsont.t
 end = struct
   (* EdDSA signatures are transmitted as 64-bytes base32
      binary-encoded objects with just the R and S values (base32_ binary-only).
@@ -111,6 +121,8 @@ end = struct
     let s = B32.encode t in
     assert (String.length s = 64);
     s
+
+  let jsont = Jsont.of_of_string ~kind:"EddsaSignature" of_b32 ~enc:to_b32
 end
 
 module RsaPublicKey = struct
@@ -130,6 +142,8 @@ module RsaPublicKey = struct
     let s = Bin.to_string bin v in
     let s = B32.encode s in
     s
+
+  let jsont = Jsont.of_of_string ~kind:"RsaPublicKey" of_b32 ~enc:to_b32
 end
 
 module RsaSignature : sig
@@ -138,6 +152,7 @@ module RsaSignature : sig
   val sign : key:Mirage_crypto_pk.Rsa.priv -> string -> t
   val of_b32 : string -> (t, string) result
   val to_b32 : t -> string
+  val jsont : t Jsont.t
 end = struct
   type t = string
 
@@ -148,11 +163,7 @@ end = struct
 
   let of_b32 s = B32.decode s
   let to_b32 t = B32.encode t
-end
-
-module HashCode = struct
-  (* 32-byte value representing a point on Curve25519. *)
-  type cs25519Point = string
+  let jsont = Jsont.of_of_string ~kind:"RsaSignature" of_b32 ~enc:to_b32
 end
 
 module RsaDenominationKey = struct